Carrier-Carrier Interaction in Proton-Conducting Perovskites: Carrier Blocking vs Trap-Site Filling

The effects of carrier-carrier interaction on the proton diffusivity in a proton-conducting perovskite, Y-doped BaZrO3, have theoretically been investigated in a first-principles manner. The proton diffusivity with the proton-proton interaction was estimated by solving the master equation under the single particle approximation. The correlation effect between successive jumps was also taken into account to estimate the proton diffusivity with more accuracy. As a result, the proton-proton interaction has two competitive effects on the proton diffusivity, i.e., the negative effect of carrier blocking and the positive effect of trap-site filling. In BaZr1-xYxO3-delta at the typical doping level (x = 0.2), the trap-site filling effect is dominant, resulting in higher proton diffusivity than that estimated without proton-proton interaction. This positive effect suggests a possible strategy for improving the proton mobility, i.e., trap-site-killer doping, which has a function to fill, annihilate, and/or destabilize the trap sites.